1. Field of the Invention
The invention relates to a method and composition for bleaching which may be incorporated into detergent formulations.
2. The Related Art
Under relatively mild temperature conditions, inorganic peroxides such as perborates and percarbonates are relatively ineffective at removing stains from substrates. This is especially a problem in the cleaning of fabrics.
A good effect can however be achieved with the aid of an organic bleach precursor or activator. Stain removal can be achieved at temperatures considerably below 60.degree. C. with such combination of chemicals. The mechanism involves reaction of the organic precursor with perhydroxyl anion generated from the inorganic peroxide. Perhydrolysis of the precursor then affords the active species which is an organic peroxo anion.
Typically, precursors are reactive esters of organic carboxylic or carbonic acids. In order to react with the inorganic peroxide (i.e. the perhydroxyl anion) to form the organic peroxo anion peracid, the ester must contain a good leaving group. Most often this leaving group is a phenol sulfonate.
Illustrative of this art is U.S. Pat. No. 4,412,934 (Chung et al). Therein is reported combinations of peroxygen bleaching compounds with the general formula RCOL. Leaving group (L) is required to have a conjugate acid of pK.sub.a in a range from 6 to about 13. Sodium nonanoyloxybenzene sulfonate (SNOBS) is noted to be particularly effective. This precursor is today part of a fabric detergent product in wide commercial use.
Illustrative of carbonate ester precursors are the disclosure of U.S. Pat. No. 4,751,015 and U.S. Pat. No. 4,818,426 each to Humphreys et al. Therein is reported a series of quaternary ammonium type precursors. Of particular efficacy is 2-(N,N,N-trimethylammonium) ethyl 4-sulfophenyl carbonate (CSPC).
A common characteristic of SNOBS and CSPC as well as other known precursors is inclusion in their structure of phenol sulfonate as the leaving group. Synthesis of phenol sulfonates is expensive. Hydrogen chloride is often a by-product. Corrosion resistant equipment is therefore necessary. Hydrogen chloride generation also demands extensive pollution control systems.
Accordingly, it is an object of the present invention to provide a precursor for use in bleaching compositions which can be economically synthesized.
Another object of the present invention is to provide a method for cleaning fabrics and other stained substrates utilizing a low cost precursor.
These and other objects of the present invention will become more readily apparent through consideration of the following detailed description and Examples.